Levetiracetam, a new antiepileptic agent: lack of in vitro and in vivo pharmacokinetic interaction with valproic acid

Application of Physiologically Based Pharmacokinetic Modeling to Characterize the Effects of Age and Obesity on the Disposition of Levetiracetam in the Pediatric Population

BACKGROUND

Levetiracetam is an antiseizure medication used for several seizure types in adults and children aged 1 month and older; however, due to a lack of data, pharmacokinetic (PK) variability of levetiracetam is not adequately characterized in certain populations, particularly neonates, children younger than 2 years of age, and children older than 2 years of age with obesity.

OBJECTIVE

This study aimed to address the gap by leveraging PK data from two prospective standard-of-care pediatric trials (n = 88) covering an age range from 1 month to 19 years, including those with obesity (64%), and applying a physiologically based PK (PBPK) modeling framework.

METHODS

A published PBPK model of levetiracetam for children aged 2 years and older was extended to pediatric patients younger than 2 years of age and patients older than 2 years of age with obesity by accounting for the obesity and age-related changes in PK using PK-Sim® software. The prospective pediatric data, along with the literature data for neonates and children younger than 2 years of age, were used to evaluate the extended PBPK models.

RESULTS

Overall, 82.4% of data fell within the 90% interval of model-predicted concentrations, with an average fold error within twofold of the accepted criteria. PBPK modeling revealed that children with obesity had lower weight-normalized clearances (0.053 L/h/kg) on average than children without obesity (0.063 L/h/kg). The effect of maturation was well-characterized, resulting in comparable PBPK-simulated, weight-normalized clearances for neonates and children younger than 2 years of age reported from the literature.

CONCLUSIONS

PBPK modeling simulations revealed that the current US FDA-labeled pediatric dosing regimen listed in the prescribing information can produce the required exposure of levetiracetam in these target populations with dose adjustments for children with obesity aged 4 years to younger than 16 years.

Development and Validation of Physiologically Based Pharmacokinetic Model of Levetiracetam to Predict Exposure and Dose Optimization in Pediatrics

Levetiracetam (Lev) is an antiepileptic drug that has been increasingly used in the epilepsy pediatric population in recent years, but its pharmacokinetic behavior in pediatric population needs to be characterized clearly. Clinical trials for the pediatric drug remain difficult to conduct due to ethical and practical factors. The purpose of this study was to use the physiologically based pharmacokinetic (PBPK) model to predict changes in plasma exposure of Lev in pediatric patients and to provide recommendations for dose adjustment. A PBPK model of Lev in adults was developed using PK-Sim® software and extrapolated to the entire age range of the pediatric population. The model was evaluated using clinical pharmacokinetic data. The results showed the good fit between predictions and observations of the adult and pediatric models. The recommended doses for neonates, infants and children are 0.78, 1.67 and 1.22 times that of adults, respectively. Moreover, at the same dose, plasma exposure in adolescents was similar to that of adults. The PBPK models of Lev for adults and pediatrics were successfully developed and validated to provide a reference for the rational administration of drugs in the pediatric population.

Levetiracetam-Induced Acute Psychosis in an Adolescent

Levetiracetam (LEV), a second-generation antiepileptic, is used as an adjunct therapy in primary generalized tonic-clonic seizures, refractory partial-onset seizures, and seizure prophylaxis after brain surgery. It is well tolerated, effective and has a convenient dosing regimen. As any other drugs, it has some adverse drug effects, including neuropsychiatric adverse effects ranging from agitation and mood symptoms to psychosis and suicide. Strong diagnostics guidelines are yet to be formulated for LEV-induced psychosis; however, complete recovery from psychotic symptoms after stopping LEV supports the possible adverse reaction from Naranjo's algorithm and, hence, the diagnosis. This case report presents a 16 years boy with focal onset generalized tonic-clonic seizure, whose drug regimen was switched to LEV, following which he had the delusion of persecution, second-person auditory hallucination, and aggressive behavior, which decreased on the 2nd day of cessation of LEV.

Physiologically based pharmacokinetic modeling of levetiracetam to predict the exposure in hepatic and renal impairment and elderly populations

Levetiracetam (LEV) is an anti-epileptic drug approved for use in various populations. The pharmacokinetic (PK) behavior of LEV may be altered in the elderly and patients with renal and hepatic impairment. Thus, dosage adjustment is required. This study was conducted to investigate how the physiologically-based PK (PBPK) model describes the PKs of LEV in adult and elderly populations, as well as to predict the PKs of LEV in patients with renal and hepatic impairment in both populations. The whole-body PBPK models were developed using the reported physicochemical properties of LEV and clinical data. The models were validated using data from clinical studies with different dose ranges and different routes and intervals of administration. The fit performance of the models was assessed by comparing predicted and observed blood concentration data and PK parameters. It is recommended that the doses be reduced to ~70%, 60%, and 45% of the adult dose for the mild, moderate, and severe renal impairment populations and ~95%, 80%, and 57% of the adult dose for the Child Pugh-A (CP-A), Child Pugh-B (CP-B), and Child Pugh-C (CP-C) hepatic impairment populations, respectively. No dose adjustment is required for the healthy elderly population, but dose reduction is required for the elderly with organ dysfunction accordingly, on a scale similar to that of adults. A PBPK model of LEV was successfully developed to optimize dosing regimens for special populations.

Therapeutic drug monitoring and the therapeutic reference range of levetiracetam for Chinese patients: Problems and issues

BACKGROUND

Levetiracetam (LEV) is widely used in the clinical monotherapy or multi-drug combination treatment of seizures due to its good tolerability and efficacy. Due to a lack of large-scale clinical studies, the relationship between levetiracetam concentrations, disease activity and adverse is unclear, limiting the usefulness of therapeutic drug monitoring (TDM) based LEV plasma levels. This study was intended to investigate factors influencing the pharmacokinetics of and the appropriate reference range of LEV concentration using available LEV TDM data.

METHODS

A rapid, accurate and sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS) method was established to determine LEV plasma concentrations. In this study, the levetiracetam plasma concentration monitoring data from 352 samples (taken from 248 patients) were used to explore the relationship between levetiracetam dose, age, combined administration with other antiseizure medications in patients with epilepsy.

RESULTS

Age and combined administration emerged as important affecting factors for the correlation of LEV concentration and dose. The correlation between concentration and dose was better in monotherapy. Combined administration may affect LEV concentration, especially when LEV is combined with oxcarbazepine, which might decrease the LEV concentration.

CONCLUSION

These findings emphasize the need to monitor LEV routinely LEV, especially among children and older adults when other antiseizure comedications are prescribed in the treatment regimen. LEV TDM is a well-established tool for the management of patients with epilepsy.

Application of PBPK modeling in predicting maternal and fetal pharmacokinetics of levetiracetam during pregnancy

Levetiracetam is currently being used to treat epilepsy in pregnant women. The plasma concentration of levetiracetam drops sharply during pregnancy, and the inability of pregnant women to maintain therapeutic concentrations can lead to seizures. This study aimed to predict the changes in fetal and maternal plasma exposure to levetiracetam during pregnancy and provide advice on dose adjustment. The physiology-based pharmacokinetics (PBPK) model was developed using PK-Sim and Mobi software, and validated following comparison of the observed plasma concentration and pharmacokinetic parameters. The levetiracetam PBPK model for mother and the fetus at various stages of pregnancy was successfully established and verified. Predictions indicated that the area under the steady-state concentration-time curve for levetiracetam decreased to 83, 62, and 67% of baseline values in the first, second, and third trimesters, respectively. Based on PBPK predictions, the recommended dose of levetiracetam is 1.2, 1.6, and 1.5 times the baseline dose in the first, second, and third trimesters, respectively, not exceeding 4000 mg/day in the third trimester due to fetal safety. The levetiracetam PBPK model for pregnancy was successfully developed and validated, and could provide alternative levetiracetam dosing regimens across the stages of pregnancy.

Physiologically-based pharmacokinetic modeling of oxcarbazepine and levetiracetam during adjunctive antiepileptic therapy in children and adolescents

Oxcarbazepine (OXZ) and levetiracetam (LEV) are two new generation anti‐epileptic drugs, often co‐administered in children with enzyme‐inducing antiepileptic drugs (EIAEDs). The anti‐epileptic effect of OXZ and LEV are linked to the exposure of OXZ’s active metabolite 10‐monohydroxy derivative (MHD) and (the parent) LEV, respectively. However, little is known about the confounding effect of age and EIAEDs on the pharmacokinetics (PKs) of MHD and LEV. To address this knowledge gap, physiologically‐based pharmacokinetic (PBPK) modeling was performed in the PK‐Sim software using literature data from children greater than or equal to 2 years of age. Age‐related changes in clearance (CL) of MHD and LEV were characterized, both in the presence (group 1) and absence (group 2) of concomitant EIAEDs. The drug‐drug interaction effect of EIAEDs was estimated as the difference in CL estimates between groups 1 and 2. PBPK modeling suggests that bodyweight normalized CL (ml/min/kg) is higher in younger children than their older counterparts (i.e., due to an influence of age). Concomitant EIAEDs further increase MHD’s CL to a fixed extent of 25% at any age, but EIAEDs’ effect on LEV’s CL increases with age from 20% (at 2 years) to 30% (at adolescence). Simulations with the maximum recommended doses (MRDs) revealed that children between 2 and 4 years and greater than 4 years, who are not on EIAEDs, are at risk of exceeding the reference exposure range for OXZ and LEV, respectively. This analysis demonstrates the use of PBPK modeling in understanding the confounding effect of age and comedications on PKs in children and adolescents.

Population Pharmacokinetics of Levetiracetam: a Systematic Review

BACKGROUND

The use of levetiracetam (LEV) has been increasing given its favorable pharmacokinetic profile. Numerous population pharmacokinetic studies for LEV have been conducted. However, there are some discrepancies regarding factors affecting its pharmacokinetic variability. Therefore, this systematic review aimed to summarize significant predictors for LEV pharmacokinetics as well as the need for dosage adjustments.

METHODS

We performed a systematic search for population pharmacokinetic studies of LEV conducted using a nonlinear-mixed effect approach from PubMed, Scopus, CINAHL Complete, and Science Direct databases from their inception to March 2020. Information on study design, model methodologies, significant covariate-parameter relationships, and model evaluation was extracted. The quality of the reported studies was also assessed.

RESULTS

A total of 16 studies were included in this review. Only two studies were conducted with a two-compartment model, while the rest were performed with a one-compartment structure. Bodyweight and creatinine clearance were the two most frequently identified covariates on LEV clearance (CLLEV). Additionally, postmenstrual age (PMA) or postnatal age (PNA) were significant predictors for CLLEV in neonates. Only three studies externally validated the models. Two studies conducted pharmacodynamic models for LEV with relatively small sample size.

CONCLUSION

Significant predictors for LEV pharmacokinetics are highlighted in this review. For future research, a population pharmacokinetic-pharmacodynamic model using a larger sample size should be conducted. From a clinical perspective, the published models should be externally evaluated before clinical implementation.

Population Pharmacokinetics of Levetiracetam: A Systematic Review

BACKGROUND

Levetiracetam has been widely used as a treatment option for different types of epilepsy in both adults and children. Because of its large between-subject variability, several population pharmacokinetic studies have been performed to identify its pharmacokinetic covariates, and thus facilitate individualised therapy.

OBJECTIVE

The aim of this review was to provide a synopsis for population pharmacokinetic studies of levetiracetam and explore the identified influencing covariates.

METHODS

We systematically searched the PubMed and Embase databases from inception to 30 June 2020. The information on study designs, target population, model characteristics, and identified covariates was summarised. Moreover, the pharmacokinetic profiles were compared among neonates, children, and adults.

RESULTS

Fourteen studies were included, among which two involved neonates, four involved children, two involved both children and adults, and six involved adults only. The median value of apparent clearance for children (0.074 L/h/kg [range 0.038-0.079]) was higher than that for adults (0.054 L/h/kg [range 0.039-0.061]). Body weight was found to significantly influence the apparent clearance and volume of distribution, whereas renal function influenced the clearance. Likewise, coadministration with enzyme-inducing antiepileptic drugs (such as carbamazepine and phenytoin) increased the drug clearance by 9-22%, whereas coadministration with valproate acid decreased it by 18.8%.

CONCLUSION

Levetiracetam dose regimen is dependent on the body size and renal function of patients. Further studies are needed to evaluate levetiracetam pharmacokinetics in neonates and pregnant women.

Pharmacokinetic Monitoring of Levetiracetam in Portuguese Refractory Epileptic Patients: Effect of Gender, Weight and Concomitant Therapy

Levetiracetam is a second-generation antiepileptic drug, widely used in the treatment of focal and generalized epilepsy due to its pharmacokinetic and safety profiles. Its pharmacokinetic monitoring is ascribed as useful to personalize its dosing regimen. The aim of the present study was to describe, for the first time, the pharmacokinetics of levetiracetam in Portuguese refractory epileptic patients. Therefore, a retrospective study was carried out on 65 Portuguese refractory epileptic patients (pharmacokinetic study: 48; validation study: 17) admitted to the Refractory Epilepsy Centre of the Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal. The pharmacokinetic parameters of levetiracetam were estimated by applying a one-compartment model with first-order absorption and elimination analysis. Male patients showed higher distribution volume (Vd/F) and oral clearance (CL/F) than female patients (median Vd/F: 52.40 L in males and 38.60 L in females, p = 0.011; median CL/F: 4.71 L/h in males and 3.91 L/h in females, p = 0.028). Higher values of Vd/F (p = 0.026) and CL/F (p = 0.003) were also found in overweight patients relative to normal weight and obese patients. Carbamazepine was the co-administered antiepileptic drug that mostly affected the pharmacokinetics of levetiracetam, increasing both Vd/F (61.30 L with carbamazepine and 39.10 L without carbamazepine, p = 0.007) and CL/F (6.71 L/h with carbamazepine and 3.91 L/h without carbamazepine, p < 0.001). The pharmacokinetics of levetiracetam was affected by gender, body mass index, and co-administration of carbamazepine. This study highlights the impact of several factors on the CL/ and Vd/F of levetiracetam when administered to refractory epileptic patients. The importance of its pharmacokinetic monitoring in clinical pharmacy stands out, thereby enabling the optimization of antiepileptic drug therapy.

Levetiracetam Induced Behavioral Abnormalities in a Patient with Seizure Disorder: A Diagnostic Challenge

Levetiracetam is a second-generation antiepileptic drug that is chemically unrelated to other antiepileptic drugs. Levetiracetam is a broad-spectrum antiseizure medication that is approved as an adjunctive therapy in the treatment of partial and generalized tonic-clonic seizures in children and adults with epilepsy. The mechanism by which Levetiracetam induces behavioral changes remains unknown. Its proposed mechanism of action involves binding to synaptic vesicle protein 2A (SV2A) and this leads to neuronal inhibition. Though, the drug has a convenient dosing regimen and is relatively well tolerated, neuropsychiatric side effects can emerge beyond the initial titration period and may be the most common reason for drug discontinuation. Levetiracetam has been reported to cause varying degrees of psychiatric adverse effects including behavioral disturbance such as agitation, hostility and psychosis, and mood symptoms and suicidality. It has been shown to induce psychiatric side effects in 13.3% of adults, with only 0.7% presenting with severe symptoms such as depression, agitation, or hostility. The prevalence rate of development of psychosis in these patients is estimated to be about 1.4%. A review of literature has demonstrated a relative correlation between Levetiracetam use and the development of neurobehavioral symptoms which is increased in predisposed individuals. This research describes the case of a 28-year-old woman with seizure disorder and a psychiatric history of schizoaffective disorder who developed aggressive behavior, paranoia, and severe hostility following administration of Levetiracetam 750 mg orally twice daily. She developed acute behavioral symptoms which were reversed with cessation of Levetiracetam. This report emphasizes the need for developing an appropriately high index of suspicion in promoting surveillance and prompt identification of behavioral adverse effects associated with Levetiracetam especially in high-risk patient population.

Off-line solid phase extraction and liquid chromatography-tandem mass spectrometry method for the quantitation of brivaracetam acid metabolites: Method validation and application to in vitro metabolism assays

Brivaracetam (BRV) is a new high affinity synaptic vesicle protein 2A ligand recently approved for adults with partial-onset seizures. As a support to in vitro metabolism assays, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method coupled to off-line solid phase extraction (SPE) was developed to quantify BRV acid metabolites, that is, BRV-AC (carboxylic derivative derived from BRV hydrolysis) and BRV-OHAC (corresponding to hydroxylated BRV-AC). The method was validated for various incubates (liver and kidney tissue homogenates and blood, all from humans) and applied to in vitro metabolism assays. The analytes were isolated from buffered samples using ISOLUTE C8 96-well SPE plates. Chromatographic separation was achieved on a Waters Atlantis T3 C18 analytical column (2.1 mm × 50 mm, 5 μm) with detection accomplished using a Waters Premier tandem mass spectrometer in positive ion electrospray and multiple reaction monitoring (MRM) mode. The standard curves, which ranged from 1.00 to 200 ng/mL for BRV-AC, BRV-OHAC, were fitted to a 1/x² weighted linear regression model. The intra-assay precision and inter-assay precision (expressed as coefficient of variation -%CV) were <8.5%, and the assay accuracy (deviation - %Dev) was within ±7.1% for the different matrices. This accurate, precise, and selective SPE/LC-MS/MS method has been successfully applied to in vitro assays aimed at characterizing the kinetics of BRV hydrolysis. BRV was found to be a better substrate for hydrolysis than its hydroxylated metabolite BRV-OH. BRV hydrolysis was detected in blood, liver and kidneys, demonstrating the broad distribution of the enzyme catalyzing the reaction.

Treatment Strategies for Dravet Syndrome

Dravet syndrome (DS) is a medically refractory epilepsy that onsets in the first year of life with prolonged seizures, often triggered by fever. Over time, patients develop other seizure types (myoclonic, atypical absences, drops), intellectual disability, crouch gait and other co-morbidities (sleep problems, autonomic dysfunction). Complete seizure control is generally not achievable with current therapies, and the goals of treatment are to balance reduction of seizure burden with adverse effects of therapies. Treatment of co-morbidities must also be addressed, as they have a significant impact on the quality of life of patients with DS. Seizures are typically worsened with sodium-channel agents. Accepted first-line agents include clobazam and valproic acid, although these rarely provide adequate seizure control. Benefit has also been noted with stiripentol, topiramate, levetiracetam, the ketogenic diet and vagal nerve stimulation. Several agents presently in development, specifically fenfluramine and cannabidiol, have shown efficacy in clinical trials. Status epilepticus is a recurring problem for patients with DS, particularly in their early childhood years. All patients should be prescribed a home rescue therapy (usually a benzodiazepine) but should also have a written seizure action plan that outlines when rescue should be given and further steps to take in the local hospital if the seizure persists despite home rescue therapy.

Determination of plasma Levetiracetam level by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS-MS) and its application in pharmacokinetics studies in neonates

BACKGROUND

Levetiracetam (LEV) is an antiepileptic drug which has good safety and efficacy in neonatal seizure (NS), a common incident in neonates with weight <1500 g. The pharmacokinetics for LEV in neonatal populations is yet to be clearly understood. In this study, we developed and validated a method for determination of LEV in plasma by liquid chromatography tandem mass spectrometry for the purpose of pharmacokinetic study.

METHODS

Plasma LEV was spiked with Lamivudine as internal standard before extraction by C18 solid-phase extraction (SPE) cartridge. Chromatography was performed using isocratic elution with mobile phase A: B (10: 90) for 2.0 min with flow rate 0.4 mL/min. The mobile phase was composed of 0.1% formic acid in 10.0 mM ammonium acetate (A) and 100% methanol (B). The injection volume was 1.0 μL and the total run time was 2.0 min. Multiple reaction monitoring (MRM) with electro spray in positive mode was used. The mass transition for LEV was 171.2/126.0 and 230.0/112.0 for IS with retention time of 0.73 and 0.72 min, respectively.

RESULTS

A calibration curve range from 0.50-80.0 μg/mL was obtained with a correlation coefficient >0.99 in the quadratic model. Precision and accuracy was within the acceptable range and the intra- and inter-day %CV for three concentrations of QCs were <10%.

CONCLUSION

This method was reliable, accurate and applicable for LEV pharmacokinetic study in neonates with seizure.

Population Pharmacokinetic Modeling of Levetiracetam in Pediatric and Adult Patients With Epilepsy by Using Routinely Monitored Data

BACKGROUND

Levetiracetam, a second-generation antiepileptic drug, is frequently used for managing partial-onset seizures. About 70% of the administered dose is excreted in urine unchanged, and dosage adjustment is recommended based on the individual's renal function. In this study, a population pharmacokinetic model of levetiracetam was developed using routinely monitored serum concentration data for individualized levetiracetam therapy.

METHODS

Patients whose serum concentrations of levetiracetam at steady-state were routinely monitored at Kyoto University Hospital from April 2012 to March 2013 were enrolled. The influence of patient characteristics on levetiracetam pharmacokinetics was evaluated using the nonlinear mixed-effects modeling (NONMEM) program.

RESULTS

A total of 583 steady-state concentrations from 225 patients were used for the analysis. The median patient age and estimated glomerular filtration rate (eGFR) were 38 (range: 1-89) years and 98 (15-189) mL·min·1.73 m, respectively. Serum concentration-time data of levetiracetam were well described by a 1-compartment model with first-order absorption. Oral clearance was allometrically related to the individual body weight and eGFR. An increase in the dose significantly increased oral clearance. No improvement in model fit was observed by including the covariate of any concomitant antiepileptic drugs. The population mean clearance for an adult weighing 70 kg and with a normal renal function was 4.8 and 5.9 L/h for 500 mg bis in die (bid) and 1500 mg bid, respectively.

CONCLUSIONS

Oral clearance allometrically related with body weight and eGFR can well predict the routine therapeutic drug monitoring data from pediatric to aged patients with varying renal function. Dosage adjustments based on renal function are effective in controlling the trough and peak concentrations in similar ranges.

The Impact of Anti-Epileptic Drugs on Growth and Bone Metabolism

Epilepsy is a common neurological disorder worldwide and anti-epileptic drugs (AEDs) are always the first choice for treatment. However, more than 50% of patients with epilepsy who take AEDs have reported bone abnormalities. Cytochrome P450 (CYP450) isoenzymes are induced by AEDs, especially the classical AEDs, such as benzodiazepines (BZDs), carbamazepine (CBZ), phenytoin (PT), phenobarbital (PB), and valproic acid (VPA). The induction of CYP450 isoenzymes may cause vitamin D deficiency, hypocalcemia, increased fracture risks, and altered bone turnover, leading to impaired bone mineral density (BMD). Newer AEDs, such as levetiracetam (LEV), oxcarbazepine (OXC), lamotrigine (LTG), topiramate (TPM), gabapentin (GP), and vigabatrin (VB) have broader spectra, and are safer and better tolerated than the classical AEDs. The effects of AEDs on bone health are controversial. This review focuses on the impact of AEDs on growth and bone metabolism and emphasizes the need for caution and timely withdrawal of these medications to avoid serious disabilities.

Levetiracetam in the Treatment of Epileptic Seizures After Liver Transplantation

After liver transplantation, patients may develop seizures or epilepsy due to a variety of etiologies. The ideal antiepileptic drugs for these patients are those with fewer drug interactions and less hepatic toxicity. In this study, we present patients using levetiracetam to control seizures after liver transplantation. We retrospectively enrolled patients who received levetiracetam for seizure control after liver transplantation. We analyzed the etiology of liver failure that required liver transplantation, etiology of the seizures, outcomes of seizure control, and the condition of the patient after follow-up at the outpatient department. Hematological and biochemical data before and after the use of levetiracetam were also collected. Fifteen patients who received intravenous or oral levetiracetam monotherapy for seizure control after liver transplantation were enrolled into this study. All of the patients remained seizure-free during levetiracetam treatment. Two patients died during the follow-up, and the other 13 patients were alive at the end of the study period and all were seizure-free without neurological sequelae that interfered with their daily activities. No patients experienced liver failure or rejection of the donor liver due to ineffective immunosuppressant medications. The dosage of immunosuppressants did not change before and after levetiracetam treatment, and there were no changes in hematological and biochemical data before and after treatment. Levetiracetam may be a suitable antiepileptic drug for patients who undergo liver transplantation due to fewer drug interactions and a favorable safety profile.

Influence of uridine diphosphate glucuronosyltransferase 2B7 -161C>T polymorphism on the concentration of valproic acid in pediatric epilepsy patients

BACKGROUND

Valproic acid (VPA) is widely used to treat various types of epilepsy. Interindividual variability in VPA pharmacokinetics may arise from genetic polymorphisms of VPA-metabolizing enzymes. This study aimed to examine the relationships between plasma VPA concentrations and the -161C>T single nucleotide polymorphism in uridine diphosphate glucuronosyltransferase (UGT) 2B7 genes in pediatric epilepsy patients.

METHODS

This study included 78 pediatric epilepsy patients carrying the cytochrome P450 (CYP) 2C9*1/*1 genotype and who were not treated with the enzyme inducers (phenytoin, phenobarbital, and carbamazepine), lamotrigine, and/or topiramate. CYP2C9*3 and UGT2B7 -161C>T polymorphisms were identified using methods based on polymerase chain reaction-restriction fragment length polymorphism. Blood samples were drawn from each patient under steady-state conditions, and plasma VPA concentrations were measured.

RESULTS

Significant differences in adjusted plasma VPA concentrations were observed between carriers of CC, CT, and TT genotypes in the UGT2B7 -161C>T polymorphism (P = 0.039). Patients with the CC genotype had lower adjusted plasma VPA concentrations than those with CT or TT genotype (P = 0.028).

CONCLUSIONS

These data suggest that the UGT2B7 -161C>T polymorphism in pediatric epilepsy patients carrying the CYP2C9*1/*1 genotype affects VPA concentration.

Rapid and simultaneous quantification of levetiracetam and its carboxylic metabolite in human plasma by liquid chromatography tandem mass spectrometry

A simple liquid chromatography tandem mass spectrometry method was developed and validated according to the guidelines of the US Food and Drug Administration and the European Medicines Agency for a simultaneous quantification of levetiracetam (LEV) and its metabolite, UCB L057 in the plasma of patients. A 0.050 mL plasma sample was prepared by a simple and direct protein precipitation with 0.450 mL acetonitrile (ACN) containing 1 µg/mL of internal standard (IS, diphenhydramine), then vortex mixed and centrifuged. A 0.100 mL of the clear supernatant was diluted with 0.400 mL water and well mixed. A 0.010 mL of the resultant solution was injected into an Agilent Zorbax SB-C18 (2.1 mm×100 mm, 3.5 µm) column with an isocratic elution at 0.5 mL/min using a mixture of 0.1% formic acid in water and ACN (40:60 v/v). Detection was performed using an AB Sciex API 3000 triple quadrupole mass spectrometer, equipped with a Turbo Ion Spray source, operating in a positive mode: LEV at transition 171.1>154.1, UCB L057 at 172.5>126.1, and IS at 256.3>167.3; with an assay run time of 2 minutes. The lower limit of quantification (LLOQ) for both LEV and UCB L057 was validated at 0.5 µg/mL, while their lower limit of detection (LOD) was 0.25 µg/mL. The calibration curves were linear between 0.5 and 100 µg/mL for both analytes. The inaccuracy and imprecision of both intra-assay and inter-assay were less than 10%. Matrix effects were consistent between sources of plasma and the recoveries of all compounds were between 100% and 110%. Stability was established under various storage and processing conditions. The carryovers from both LEV and UCB L057 were less than 6% of the LLOQ and 0.13% of the IS. This assay method has been successfully applied to a population pharmacokinetic study of LEV in patients with epilepsy.

Valproic acid, but not levetiracetam, selectively decreases HDAC7 and HDAC2 expression in human ovarian cancer cells

Histone deacetylases (HDACs) are often overexpressed in cancer cells, leading to altered expression and activity of numerous proteins involved in carcinogenesis. Recent evidence suggests that expression of class I HDACs is increased in ovarian carcinomas and plays a significant role in carcinogenesis and resistance to chemotherapeutic agents. Two compounds, valproic acid (VPA) and levetiracetam (LEV), exhibit HDAC inhibitor (HDACI) activity in various cell types, but data concerning their activity in ovarian cancer are lacking. Here we compared the effects of VPA and LEV as HDACIs, using a human ovarian cancer cell line, OVCAR-3. Cells were cultured with VPA or LEV at concentrations between 1 and 10 mM for 1-24h. HDAC activity was determined by fluorometric assay and confirmed by western blotting. Expression of HDAC genes was determined by real-time PCR and HDAC proteins expression was evaluated by western blotting. Additionally, we used high-performance liquid chromatography to determine whether OVCAR-3 cells can metabolize LEV to its major metabolite, 2-pyrrolidinone-n-butyric acid (PBA), which might exert HDACI activity. LEV, however, had no apparent effect on HDAC activity, or gene and protein expression. The OVCAR-3 cell line was able to metabolize LEV to PBA, but the effect was small. Our observations suggest that VPA should be considered as a possible adjunctive drug in ovarian cancer treatment.

Levetiracetam: Relative Bioavailability and Bioequivalence of a 10% Oral Solution (750 mg) and 750-mg Tablets

Levetiracetam, an antiepileptic drug, is used worldwide as an adjunctive treatment for partial-onset seizures. The availability of a new oral solution formulation would provide an additional treatment option for patients who have difficulty swallowing tablets. A phase I single-center, randomized, open-label, two-way crossover, single-dose study was conducted to confirm that a 10% oral solution of levetiracetam was bioequivalent to the 750-mg oral tablet and to characterize its pharmacokinetics. Each of 24 healthy subjects received a single oral 750-mg dose of the randomized levetiracetam formulation (7.5 mL of 10% solution or 750-mg tablet) on day 1 and a single oral dose of the alternate formulation on day 8. Serial blood samples were collected from 0 to 36 hours after each dose administration for determination of plasma levetiracetam concentrations. Pharmacokinetic parameters were calculated, and bioequivalence of the two formulations was evaluated. The mean levetiracetam plasma concentration-time curves and pharmacokinetic parameters essentially were identical for the oral 10% solution and tablet and consistent with previously reported levetiracetam pharmacokinetics. The 90% confidence limits of the geometric mean ratio of the two formulations for area under the plasma concentration-time curve from time 0 to infinity, area under the plasma concentration-time curve from time 0 to last measurable time point, and maximum plasma concentration were within the 80% to 125% range, demonstrating bioequivalence of the two formulations. Both levetiracetam formulations were well tolerated. The levetiracetam 10% oral solution is a bioequivalent, well-tolerated alternative to the tablet formulation in patients who have difficulty swallowing.

A seven-day study of the pharmacokinetics of intravenous levetiracetam in neonates: marked changes in pharmacokinetics occur during the first week of life

INTRODUCTION

Levetiracetam (LEV) is increasingly used in the treatment of neonatal seizures. The aim of this study was to determine pharmacokinetics in neonates with seizures and to obtain preliminary safety and efficacy data.

METHODS

Eighteen term neonates with seizures persisting after 20 mg/kg of phenobarbital received intravenous LEV for 1 wk. LEV was administered as a 20 or 40 mg/kg bolus followed by 5-10 mg/kg/d. Pharmacokinetic data were analyzed using a nonlinear mixed-effects population approach. Continuous electroencephalogram monitoring allowed preliminary assessment of the efficacy of LEV in this population.

RESULTS

LEV clearance (CL) increased from a mean of 0.7 ml/min/kg (SD 0.27 ml/min/kg) on day 1 to 1.33 ml/min/kg (SD 0.35 ml/min/kg) by day 7. Mean half-life was 18.5 h (SD 7.1 h) on day 1 of the study and decreased to 9.1 h (SD 2.0 h) by day 7. The mean volume of distribution was 1.01 l/kg (SD 0.13 l/kg). No study-related serious adverse events were observed.

DISCUSSION

CL of LEV in neonates was higher than expected on the basis of immature renal function in term infants and increased significantly during the first week of life. More frequent dosing of LEV is needed in term infants to maintain serum concentrations in the range seen in children and adults.

Effect of levetiracetam on cardiac repolarization in healthy subjects: a single-dose, randomized, placebo- and active-controlled, four-way crossover study

BACKGROUND

Nonantiarrhythmic drugs may have the potential to prolong the QT interval, leading to potentially fatal ventricular tachycardias, including torsades de pointes.

OBJECTIVE

This study evaluated the potential of the newer-generation, multiple-action antiepileptic drug levetiracetam, which binds to the synaptic vesicle protein SV2A, to affect cardiac repolarization, as detected by prolongation of the QT/corrected QT (QTc) interval.

METHODS

This was a single-dose, randomized, placebo- and active-controlled, 4-way crossover study in healthy subjects. Subjects were randomly allocated to 1 of 4 different administration sequences. Each sequence included 3 double-blind treatments (levetirace-tam 1000 mg, levetiracetam 5000 mg, and placebo) and 1 open-label treatment (moxifloxacin 400 mg). Triplicate electrocardiograms (ECGs) were obtained at baseline and at various time points over 24 hours after each treatment using continuous Holter monitoring. ECGs were read centrally in a blinded manner. Blood samples for the determination of plasma concentrations of levetiracetam and moxifloxacin were collected before dosing and at 0.5, 1, 1.5, 2, 4, 6, 12, and 24 hours after dosing, within 5 minutes after the ECG recordings. The QT interval was corrected for heart rate using a sex- and study-specific correction (QTc(ss)) as the primary outcome measure and Fridericia's correction (QTc(F))as a secondary outcome measure. The primary analysis was performed on the time-matched, baseline-subtracted QTc(ss) (DeltaQTc(ss)). The maximum DeltaQTc(ss) difference between each active treatment and placebo (DeltaDeltaTc(ss)) was derived from a mixed-effect analysis of variance. Clinical laboratory tests, standard 12-lead ECGs, and vital signs were monitored at regular intervals. Spontaneously reported adverse events were recorded throughout the study.

RESULTS

Fifty-two healthy, nonsmoking subjects (26 men, 26 women; 37 white, 9 black, 3 Hispanic, and 3 Asian/Pacific Islander) with a mean (SD) age of 28.4 (7.5) years (range, 18-45 years) and a mean weight of 71.5 (12.6) kg (range, 49-103 kg) participated in the study. Levetiracetam did not significantly prolong the QTc(ss). The upper bound of the 1-sided 95% CI for the maximum DeltaDeltaTc(ss) was 8.0 milliseconds for levetiracetam 1000 mg and 8.1 milliseconds for levetiracetam 5000 mg, with mean estimates of 4.0 and 4.1 milliseconds, respectively; similar results were obtained for the maximum DeltaDeltaQTc(F). Moxifloxacin significantly prolonged the QTc(ss), with a lower bound of the 1-sided 95% CI for the maximum DeltaDeltaQTc(ss) of 3.7 milliseconds and a mean estimate of 7.7 milliseconds. There was no statistically significant relationship between measured DeltaQTc(ss) and the levetiracetam plasma concentration, whereas a significant linear relationship was observed between measured DeltaQTc(ss) and the moxifloxacin plasma concentration (slope estimate: 4.4 milliseconds/[microg/mL]); 95% CI, 3.2-5.7; P < 0.001). No unexpected safety concerns arose based on reported adverse events, clinical laboratory evaluations, physical examinations, vital signs, or ECG monitoring during the course of the study.

CONCLUSION

This randomized, placebo- and active-controlled study in healthy adult subjects found no clinically relevant changes in the QTc interval after a single levetiracetam dose of 1000 or 5000 mg.

Physiology-based simulations of a pathological condition: prediction of pharmacokinetics in patients with liver cirrhosis

BACKGROUND

Liver cirrhosis is a progressive disease characterized by loss of functional hepatocytes with concomitant connective tissue and nodule formation in the liver. The morphological and physiological changes associated with the disease substantially affect drug pharmacokinetics. Whole-body physiologically based pharmacokinetic (WB-PBPK) modelling is a predictive technique that quantitatively relates the pharmacokinetic parameters of a drug to such (patho-)physiological conditions.

OBJECTIVE

To extend an existing WB-PBPK model, based on the physiological changes associated with liver cirrhosis, which allows for prediction of drug pharmacokinetics in patients with liver cirrhosis.

METHODS

The literature was searched for quantitative measures of the physiological changes associated with the presence of Child-Pugh class A through C liver cirrhosis. The parameters that were included were the organ blood flows, cardiac index, plasma binding protein concentrations, haematocrit, functional liver volume, hepatic enzymatic activity and glomerular filtration rate. Predictions of pharmacokinetic profiles and parameters were compared with literature data for the model compounds alfentanil, lidocaine (lignocaine), theophylline and levetiracetam.

RESULTS

The predicted versus observed plasma concentration-time profiles for alfentanil and lidocaine were similar, such that the pharmacokinetic changes associated with Child-Pugh class A, B and C liver cirrhosis were adequately described. The theophylline elimination half-life was greatly increased in Child-Pugh class B and C patients compared with controls, as predicted by the model. Levetiracetam urinary excretion was consistently reduced with disease progression and very closely resembled observed values.

CONCLUSION

Consideration of the physiological differences between healthy individuals and patients with liver cirrhosis was important for the simulation of drug pharmacokinetics in this compromised group. The WB-PBPK model was altered to incorporate these physiological differences with the result of adequate simulation of drug pharmacokinetics. The information provided in this study will allow other researchers to further validate this liver cirrhosis model within a WB-PBPK model.

Levetiracetam in the treatment of epilepsy

Epilepsy is a common chronic disorder that requires long-term antiepileptic drug therapy. Approximately one half of patients fail the initial antiepileptic drug and about 35% are refractory to medical therapy, highlighting the continued need for more effective and better tolerated drugs. Levetiracetam is an antiepileptic drug marketed since 2000. Its novel mechanism of action is modulation of synaptic neurotransmitter release through binding to the synaptic vesicle protein SV2A in the brain. Its pharmacokinetic advantages include rapid and almost complete absorption, minimal insignificant binding to plasma protein, absence of enzyme induction, absence of interactions with other drugs, and partial metabolism outside the liver. The availability of an intravenous preparation is yet another advantage. It has been demonstrated effective as adjunctive therapy for refractory partial-onset seizures, primary generalized tonic-clonic seizures, and myoclonic seizures of juvenile myoclonic epilepsy. In addition, it was found equivalent to controlled release carbamazepine as first-line therapy for partial-onset seizures, both in efficacy and tolerability. Its main adverse effects in randomized adjunctive trials in adults have been somnolence, asthenia, infection, and dizziness. In children, the behavioral adverse effects of hostility and nervousness were also noted. Levetiracetam is an important addition to the treatment of epilepsy.

Lack of Pharmacokinetic Interaction of Levetiracetam on Carbamazepine, Valproic Acid, Topiramate, and Lamotrigine in Children with Epilepsy

PURPOSE

To determine whether levetiracetam (LEV) affects plasma concentrations of carbamazepine, valproic acid, topiramate, and lamotrigine in children with epilepsy.

METHODS

The potential for interaction of LEV with other antiepileptic drugs (AEDs) was assessed using plasma drug levels obtained in a randomized placebo-controlled phase III trial of adjunctive LEV in children receiving one or two concomitant AEDs. Multiple plasma AED levels at baseline and during adjunctive treatment with LEV or placebo were compared by repeated measures analysis of covariance and mean concentration ratios (treatment/baseline) were estimated with their 90% confidence intervals (CI).

RESULTS

The study population included 187 children receiving any concomitant AED alone or in combination. The geometric mean concentrations at baseline and during LEV treatment were carbamazepine 8.4 microg/ml versus 8.1 microg/ml (coefficient of variation, CV = 30%; n = 35); valproic acid 83.8 versus 82.5 microg/ml (CV = 38%; n = 23); topiramate 7.3 versus 7.2 microg/ml (CV = 82%; n = 28); lamotrigine 8.2 versus 7.7 microg/ml (CV = 62%; n = 22). For each AED, the mean concentration ratios (LEV/baseline) and their 90% CIs showed that AED concentrations were unaffected by concomitant LEV administration. No differences were observed between LEV and placebo.

CONCLUSIONS

LEV does not affect plasma concentrations of carbamazepine, valproic acid, topiramate, or lamotrigine in children with epilepsy.

Effect of Age and Comedication on Levetiracetam Pharmacokinetics and Tolerability

PURPOSE

To compare pharmacokinetics and tolerability of levetiracetam (LEV) in older versus younger adults.

METHODS

As part of the Columbia Antiepileptic Drug Database, we retrospectively studied the pharmacokinetics and tolerability of LEV in patients who had been seen as an outpatient at our center during a 4-year period. We compared apparent clearance (CL) of LEV in the youngest (16-31 years; n=151) and oldest (55-88 years; n=157) quartile of 629 adult outpatients who had taken LEV. We also analyzed the frequency of adverse effects leading to dose change or discontinuation ("intolerability") and specific adverse effects in the younger versus older adults. One-year retention was determined for younger and older adults newly started on LEV at our center.

RESULTS

Mean LEV CL differed significantly between older (46.5 ml/h/kg) and younger adults (78.3 ml/h/kg). On average, older patients had a 40% lower LEV CL than younger patients. Comedication with an enzyme-inducing antiepileptic drug (EIAED; mostly carbamazepine) was associated with a 24% higher clearance of LEV compared to those who were not on EIAEDs. This difference was 37% in a subgroup of patients whose LEV CL was compared while they were on and off EIAEDs. Stepwise linear regression identified younger age and comedication with an EIAED as significant predictors of increased LEV CL. A total of 34.3% of the 629 patients (31.7% of younger vs. 40.7% of older patients; p=0.16) reported intolerability to LEV on at least one occasion. This difference in tolerability reached significance in the group of patients newly started on LEV (26.3% vs. 41.0%; p=0.017). Drowsiness and psychiatric/behavioral side effects were the most common adverse effects associated with LEV use in both age groups. One-year retention was 72% in the older group vs. 54% in the younger group (not significant).

CONCLUSION

Older adults have lower CL than younger adults and require a mean 40% lower dose of LEV to achieve the same serum level. Comedication with an EIAED increases LEV CL by 24-37%. Younger adults tolerate LEV better than older adults, but 1-year retention was (nonsignificantly) higher in the older group.

Prospective assessment of levetiracetam pharmacokinetics during dose escalation in 4- to 12-year-old children with partial-onset seizures on concomitant carbamazepine or valproate

PURPOSE

To assess the multiple-dose pharmacokinetics of levetiracetam and its major metabolite ucb L057 in children with partial-onset seizures and determine whether it is affected by adjunctive carbamazepine or valproate. To correlate levetiracetam concentrations in plasma and saliva and to assess its safety and clinical response.

METHODS

Design was an open-label, multicenter study. Twenty-one children (4-12 years old) with epilepsy taking carbamazepine (13) or valproate (8) received adjunctive levetiracetam. Levetiracetam was initiated at 20 mg/(kg day) and titrated at 2-week intervals to 40 and then 60 mg/(kg day). Twelve-hour pharmacokinetics were determined at the end of each 2-week period. Efficacy was estimated from the partial seizure frequency per week and Global Evaluation Scale.

RESULTS

Levetiracetam was rapidly absorbed following oral dosing, with median t(max) of 0.5 h. Dose proportional increases were observed for C(max) and AUC((0-12)) over the dose range; t(1/2) was 4.9 h. Pharmacokinetics of levetiracetam and ucb L057 were not markedly different with concomitant carbamazepine or valproate; clearance was only 7-13% faster and AUC was decreased by only 15-24% in those on carbamazepine compared to valproate. Levetiracetam did not affect trough carbamazepine or valproate. Concentration in saliva and plasma were strongly correlated. Seizure frequency declined by 50% or more in 43% of subjects in the intent-to-treat population (n=21) and in 56% of those with seizures at baseline (n=16). Marked or moderate improvement occurred in 80% and 75% of patients based on Global Evaluation Scale ratings by investigators and parents/guardians, respectively. Levetiracetam was well tolerated.

CONCLUSION

Levetiracetam exhibits simple pharmacokinetics in children, with rapid absorption and dose-proportional kinetics. Small but not clinically relevant differences were observed between subjects receiving carbamazepine and valproate, suggesting significant dose adjustment is usually not necessary. This substantiates prior assessments that levetiracetam clearance is higher in children than adults, necessitating a higher dose in children on a mg/kg basis, and suggests it is useful add-on therapy for children with partial-onset seizures regardless of baseline therapy.

In situ metabolism of levetiracetam in blood of patients with epilepsy

PURPOSE

Although levetiracetam undergoes minimum metabolism, B-esterases have been identified in whole blood that are capable of metabolising levetiracetam. The present study was designed to ascertain any variability in levetiracetam blood concentrations that could be attributed to in situ metabolism and which could impact on the utility of such concentration measurements in guiding therapeutic management.

METHODS

Blood samples were collected from 40 patients that were prescribed levetiracetam. Sera (Groups 1 and 2) or whole blood (Groups 3 and 4) were compared. Paraoxan, an inhibitor of B-esterase activity, was added to samples assigned to Groups 2 and 4. Samples within each group were assigned to Time 0 (frozen within 30 min of sample collection), Time 2 days and Time 7 days (samples kept at ambient temperature for 2 and 7 days).

RESULTS

For serum samples, mean levetiracetam concentrations at Time 2 days and Time 7 days were indistinguishable from Time 0, regardless of whether B-esterase activity was inhibited on not. In contrast, for whole blood, in the absence of B-esterase inhibition, mean levetiracetam concentrations declined over time (11% and 29%; 2 and 7 days) compared to baseline values. In the presence of B-esterase inhibitor, mean levetiracetam concentrations at 2 days were indistinguishable from baseline values, although at 7 days values declined by 4%.

CONCLUSIONS

If therapeutic monitoring of levetiracetam is to be undertaken, serum should be the matrix of choice and that whole blood should be separated as soon as possible after patient sampling so as to minimize in situ levetiracetam metabolism which could result in spuriously low concentrations and substantial intrapatient variability.

Population Pharmacokinetics of??Levetiracetam in Japanese and??Western Adults

OBJECTIVE

To assess the population pharmacokinetics of levetiracetam, a second-generation antiepileptic drug, in adult Japanese and Western populations.

METHODS

Data were pooled from ten matched clinical trials conducted in Japan and in Europe and the USA, in which levetiracetam was administered orally to healthy subjects and subjects with epilepsy. Overall, 5408 plasma concentrations were available from 524 subjects in six clinical pharmacology studies and two confirmatory and two long-term safety studies of add-on treatment for partial epilepsy. A one-compartment open model with first-order absorption and elimination was fitted to the plasma concentrations using nonlinear mixed-effects modelling with first-order estimation.

RESULTS

Ethnicity had no statistically significant effect on the pharmacokinetics of levetiracetam in the presence of the other covariates. Bodyweight, sex, creatinine clearance and concomitant intake of enzyme inducers or valproic acid had a statistically significant effect on apparent plasma clearance of levetiracetam. Bodyweight, disease and valproic acid had a statistically significant effect on the volume of distribution. Levetiracetam exposure (the area under the plasma concentration-time curve over the 12-hour dosing interval at steady state) was 12% higher in females than in males. Decreasing bodyweight from 70 kg to 40 kg was predicted to increase exposure by 16%, while halving creatinine clearance was predicted to increase exposure by 10%. Enzyme inducers reduced exposure by 8%, while valproic acid resulted in a 23% increase in exposure. The latter effect was assumed to arise from the known association between valproic acid and increased body fat, since levetiracetam is negligibly metabolised by cytochrome P450 enzymes.

CONCLUSIONS

Population pharmacokinetic analysis points to the absence of ethnic differences in the pharmacokinetics of levetiracetam between Japanese and Western populations, other than those arising from bodyweight differences. Small, clinically non-relevant differences between individual demographic characteristics suggest that dose adjustment is usually not necessary.

Single-dose bioavailability of levetiracetam intravenous infusion relative to oral tablets and multiple-dose pharmacokinetics and tolerability of levetiracetam intravenous infusion compared with placebo in healthy subjects

BACKGROUND

Antiepileptic drugs are usually administere dorally, but alternative routes of drug delivery may be required when oral administration is not feasible.

OBJECTIVE

The purpose of this study was to evaluate the single-dose bioavailability of an IV formulation of levetiracetam relative to oral tablets and the multiple-dose tolerability and pharmacokinetics of this formulation compared with placebo in healthy subjects.

METHODS

This study consisted of 2 phases. Subjects entered the first phase, which was a single-dose, randomized, open-label, 2-way crossover bioavailability comparison of a 15-minute IV infusion of levetiracetam 1,500 mg and three 500-mg oral tablets. Subjects then entered the second phase, a multiple-dose, randomized, double-blind, placebo-controlled (2:1), parallel-group tolerability and pharmacokinetic study, in which they received 9 successive doses of levetiracetam 1,500 mg IV or placebo at 12-hour intervals. Plasma levetiracetam concentrations were determined by gas chromatography with nitrogen-phosphorus detection. The comparison of bioavailability was based on the 90% CIs around the geometric mean ratios for AUC and C(max) (IV/oral).

RESULTS

Eighteen subjects (9 men, 9 women) participated in the study. All subjects were white. Their mean (SD) age was 35.0 (9.3) years, mean weight 73.3 (14.2) kg, and mean body mass index 23.9 (2.5) kg/m(2). After a single dose, the IV infusion and oral tablet were similar in terms of C(max) (50.5 and 47.7 microg/mL, respectively) and AUC (392.4 and 427.9 pg x h/mL). The geometric mean IV/oral ratios were 92.2 (90 % CI, 89.0-95.6) for AUC and 103.7 (90% CI, 91.6-117.4) for C(max) indicating that the IV and oral formulations were bioequivalent. After multiple twice-daily infusions, steady state was reached within 48 hours. Seventeen (94%) of 18 subjects had >or=1 treatment-emergent adverse event after single-dose administration. During the single-dose phase, the incidence of treatment-emergent adverse events was 89% (16/18) for the IV formulation and 72% (13/18) for the oral tablets; during the multiple-dose phase, the incidence of treatment-emergent adverse events was 67% (8/12) in the IV levetiracetam group and 33% (2/6) in the placebo group. The most common adverse events in the single-dose phase were somnolence (61% IV vs 28% oral) and postural dizziness (17% vs 39%, respectively). The most common adverse events with IV levetiracetam in the multiple-dose phase were also somnolence (33% vs 17% placebo) and postural dizziness (25% vs 0% placebo).

CONCLUSIONS

In these healthy subjects, single doses of levetiracetam 1,500 mg administered as a 15-minute IV infusion and as oral tablets were bioequivalent. General and local tolerability during multiple dosing were good. Steady state was reached within 48 hours. Despite the limitations of a study of short duration and small size conducted in healthy subjects, the findings suggest that use of a 15-minute IV infusion of levetiracetam should be further investigated.

Levetiracetam Intravenous Infusion: A Randomized, Placebo-controlled Safety and Pharmacokinetic Study

PURPOSE

The primary objective of this placebo-controlled study was to evaluate the safety and tolerability of levetiracetam (LEV) administered intravenously (IV) at higher doses and/or at a faster infusion rate than proposed. The secondary objective was to assess LEV pharmacokinetics.

METHODS

Single ascending doses of LEV administered by IV infusion (2,000, 3,000, 4,000 mg over 15 min; 1,500, 2,000, 2,500 mg over 5 min) were evaluated in 48 healthy subjects in a randomized, single-blind, placebo-controlled study.

RESULTS

All randomized subjects completed the study. Adverse events reported after IV administration of LEV (<or=4,000 mg infused over 15 min and <or=2,500 mg infused over 5 min) were primarily related to the CNS (dizziness, 52.8%; somnolence, 33.3%; fatigue, 11.1%; headache, 8.3%) and were consistent with the established safety profile for the oral formulation. Safety profiles were similar for each dose level of LEV and for both IV infusion rates, with no clear relation noted between incidence of adverse events and IV dose level or infusion rate. The pharmacokinetics of LEV administered by IV infusion was comparable across all dose groups and infusion rates. Respective geometric means (coefficient of variation) for 4,000 mg administered over 15 min and 2,500 mg infused over 5 min were maximum plasma concentration, 145 (24.6%) and 94.3 (36.2%) mug/ml; area under the plasma concentration-time curve, 1,239 (19.2%) and 585 (9.6%) mug/h/ml; terminal half-life, 8.0 (14.5%) and 7.0 (12.7%) h.

CONCLUSIONS

LEV administered by IV infusion at dosages and/or infusion rates higher than those proposed was well tolerated in healthy subjects, and the pharmacokinetic profile was consistent with that for LEV administered orally.

Levetiracetam Efficacy in Epileptic Syndromes with Continuous Spikes and Waves during Slow Sleep: Experience in 12 Cases

PURPOSE

To assess the add-on efficacy of levetiracetam on the EEG, behavior, and cognition of children with continuous spikes and waves during slow sleep (CSWS).

METHODS

Charts of children with behavioral and/or cognitive deterioration associated with CSWS who received levetiracetam at 50 mg/kg/day as add-on treatment were retrospectively reviewed. Awake and sleep EEG recordings and detailed neuropsychological and behavioral assessments were available at baseline and 2 months after levetiracetam initiation. In children showing clinical and/or electrophysiological improvement after 2 months, levetiracetam was continued with a new evaluation at 1 year.

RESULTS

Twelve patients were included (9 cryptogenic and 3 symptomatic cases). Seven patients (58.3%) showed improvement of EEG record. Among these seven patients, neuropsychological evaluation was improved in three, and in the other four patients, not testable because of severe cognitive impairment, behavior was improved. Two patients improved in neuropsychological evaluation despite the lack of EEG improvement. Eight patients (66.6%) continued levetiracetam treatment after 2 months. After 1 year, four patients were still on levetiracetam, two because sustained effect on EEG and behavior and the two others because improvement in neuropsychological testing despite unchanged EEG. Levetiracetam was discontinued in the other four patients because of neuropsychological or behavioral deterioration associated with CSWS pattern, between 9 and 11 months after treatment initiation.

CONCLUSIONS

This retrospective study suggests that levetiracetam has a positive effect on the EEG, the behavior, and the cognition of patients with epilepsy and CSWS. Additional studies are warranted in order to assess the place of this drug in these epileptic conditions.

Levetiracetam: treatment in epilepsy

A large number of new antiepileptic drugs (AEDs) have become available over the last 10 years. Results from placebo-controlled clinical trials and community-based practice have demonstrated that levetiracetam has a broad spectrum of activity in suppressing seizures as add-on treatment and monotherapy and that it is safe and well-tolerated. Levetiracetam also has a favourable pharmacokinetic profile characterised by rapid and nearly complete absorption, very low potential for drug interactions and a prolonged pharmacodynamic effect that permits twice-daily dosing. Although, the mechanism of action of levetiracetam is not completely understood, preclinical studies suggest that it may have antiepileptogenic and neuroprotective effects, with the potential to slow or arrest disease progression.

Effect of levetiracetam on the pharmacokinetics of adjunctive antiepileptic drugs: A pooled analysis of data from randomized clinical trials

The purpose of this study was to determine the influence of levetiracetam on the steady-state serum concentrations of other commonly used antiepileptic drugs (AEDs). Serum AED concentrations were measured at baseline and after adjunctive therapy with levetiracetam (1000-4000 mg/day) or placebo in four phase III trials in patients with refractory partial epilepsy receiving stable AED dosages. The data were pooled, and repeated measures covariance analysis was used to calculate the ratio (and 90% confidence intervals) of the geometric mean serum drug concentrations during adjunctive levetiracetam therapy relative to baseline. Levetiracetam did not increase or decrease mean steady-state serum concentrations of carbamazepine, phenytoin, valproic acid, lamotrigine, gabapentin, phenobarbital, or primidone. For each of these AEDs, the 90% confidence interval of the geometric mean drug concentrations ratio was included within the 80-125% bioequivalence range. Serum concentrations of these AEDs did not change over time after adjunctive levetiracetam therapy, irrespective of the dosage of levetiracetam used. For vigabatrin, there was no evidence for a significant change in serum drug concentration after the addition of levetiracetam, but the number of observations was too small for the limits of the confidence interval to fall within the 80-125% range. Thus, adjunctive therapy with levetiracetam does not influence the steady-state serum concentrations of concomitantly administered carbamazepine, phenytoin, valproic acid, lamotrigine, gabapentin, phenobarbital, or primidone. Consequently, no need for adjusting the dosages of these AEDs is anticipated when levetiracetam is added on or removed from a patient's therapeutic regimen.

Benefit-Risk Assessment of Levetiracetam in the Treatment of Partial Seizures

Levetiracetam is a novel antiepileptic drug that has been demonstrated as being effective in the management of partial seizures. It is rapidly and completely absorbed after oral administration and it is predominantly eliminated as unchanged drug in the urine. Its metabolism is independent of the cytochrome P450 enzyme system, nor does it induce cytochrome P450 enzymes. As a result of its pharmacokinetic features, levetiracetam has not been demonstrated to interact with other drugs in either direction. In double-blind, placebo-controlled trials, all the levetiracetam dosages tested were effective, including 1000 mg/day, 2000 mg/day and 3000 mg/day. The ineffective dose is not known. Efficacy seemed to be maintained in long-term studies, with no evidence of tolerance. In major double-blind, placebo-controlled trials discontinuation rates because of adverse events were 6.9-10.9% for levetiracetam-treated patients (all doses) compared with 5.3-8.6% for placebo-treated patients. The most common adverse events that differed between treatment groups and placebo control groups were somnolence, asthenia, dizziness and, in the US study, infection. Since levetiracetam was marketed, behavioural effects have been reported, namely irritability, agitation, anger and aggressive behaviour. These adverse effects are more likely in learning disabled individuals, those with prior psychiatric history and those with symptomatic generalised epilepsy. Overall, the risk has been estimated at 12-15%. Laboratory parameters overall seem to be not significantly affected by levetiracetam, although slight trends to lower white and red blood cell counts were detected in the studies. No organ toxicity has been described so far, with patient exposures exceeding 500,000. In summary, levetiracetam exhibits a very favourable safety profile in patients with partial onset seizures. Whereas somnolence, asthenia and dizziness were the most prominent adverse effects in clinical trials, behavioural adverse effects have generally been the most common reason for drug discontinuation in clinical practice.

Progress report on new antiepileptic drugs: a summary of the Seventh Eilat Conference (EILAT VII)

The Seventh Eilat Conference on New Antiepileptic Drugs (AEDs) (EILAT VII) took place in Villasimius, Sardinia, Italy from the 9th to 13th May 2004. Basic scientists, clinical pharmacologists and neurologists from 24 countries attended the conference,whose main themes included advances in pathophysiology of drug resistance, new AEDs in pediatric epilepsy syndromes, modes of AED action and spectrum of adverse effects and a re-appraisal of comparative responses to AED combinations. Consistent with previous formats of this conference, the central part of the conference was devoted to a review of AEDs in development, as well as updates on second-generation AEDs. This article summarizes the information presented on drugs in development, including atipamezole, BIA-2-093, fluorofelbamate, NPS 1776, pregabalin, retigabine, safinamide, SPM 927, stiripentol, talampanel,ucb 34714 and valrocemide (TV 1901). Updates on felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, tiagabine,topiramate, vigabatrin, zonisamide, new oral and parenteral formulations of valproic acid and SPM 927 and the antiepileptic vagal stimulator device are also presented.

Levetiracetam Therapeutic Monitoring in Patients with Epilepsy

The authors assessed the effect of concomitant antiepileptic therapy on steady-state plasma concentrations of the new anti-epileptic drug (AED) levetiracetam in a cohort of 100 adult patients with epilepsy. On the basis of concomitant AEDs, patients were divided into two groups, otherwise comparable for age, gender, weight-adjusted daily dose of levetiracetam, and dosing frequency: group A (n = 65), receiving levetiracetam plus AED inducers of cytochrome P450 (CYP) metabolism, such as carbamazepine, phenobarbital, and phenytoin; group B (n = 35), receiving levetiracetam plus AEDs without inducing properties of CYP metabolism, namely valproic acid and lamotrigine. Plasma levetiracetam concentrations were measured by HPLC with spectrophotometric detection. Median morning trough levetiracetam plasma concentrations were significantly lower in patients of group A than in patients of group B (10.4 microg/mL versus 14.7 microg/mL, P < 0.001). Median weight-normalized levetiracetam apparent oral clearance (CL/F) was 1.3-fold in patients receiving AED inducers compared with patients on AED noninducers (1.93 versus 1.45 mL x min(-1) x kg, P < 0.001). No gender-related difference was observed in CL/F values. Levetiracetam plasma concentrations were linearly related to daily drug doses, regardless of concomitant AED therapy, over a dose range from 500 to 5000 mg/d, although at a given daily dose an appreciable interpatient variability was observed in matched plasma drug concentrations. Concomitant AED inducers can contribute to variability in levetiracetam disposition in patients with epilepsy. The observed differences were moderate and possibly of minor clinical significance.

The Activity of Antiepileptic Drugs as Histone Deacetylase Inhibitors

PURPOSE

Valproic acid (VPA), one of the widely used antiepileptic drugs (AEDs), was recently found to inhibit histone deacetylases (HDACs). HDAC inhibitors of a wide range of structures, such as hydroxamic acids, carboxylic acids, and cyclic tetrapeptides, have various effects on transformed and nontransformed cells, including neuromodulation and neuroprotection. The aim of this study was to assess comparatively the activity of traditional and newer AEDs as HDAC inhibitors.

METHODS

After incubation of HeLa cells with the tested AEDs, histone hyperacetylation was assessed by immunoblotting with an antibody specific to acetylated histone H4. Direct HDAC inhibition by AEDs was estimated by using HeLa nuclear extract as an HDACs source and an acetylated lysine substrate.

RESULTS

We found that in addition to VPA, topiramate (TPM) inhibited HDACs with apparent Ki values of 2.22 +/- 0.67 mM. Although levetiracetam (LEV) had no direct effect on HDACs, its major carboxylic acid metabolite in humans, 2-pyrrolidinone-n-butyric acid (PBA), inhibited HDACs with Ki values of 2.25 +/- 0.78 mM. The AEDs LEV, phenobarbital, phenytoin, carbamazepine, ethosuximide, gabapentin, and vigabatrin did not inhibit HDACs. The compounds that directly inhibited HDACs also induced the accumulation of acetylated histone H4 in HeLa cells. The effects of TPM and PBA on histone acetylation were significant at 0.25 mM and 1 mM, respectively.

CONCLUSIONS

We found that in addition to VPA, the newer AED TPM and the major metabolite of LEV, PBA, are able to induce histone hyperacetylation in human cells, although with lower potencies than VPA.

Serum concentrations of Levetiracetam in epileptic patients: the influence of dose and co-medication

Levetiracetam (LEV) is a new antiepileptic drug approved as add-on therapy. Previous studies indicated that LEV has no relevant interactions with other antiepileptic drugs. The aim of this study was to investigate the influence of LEV dose, age, and co-medication on the serum concentration of LEV. In total, 363 samples of 297 inpatients who fulfilled the inclusion criteria (e.g., trough concentration, body weight available) were investigated. A patient was considered twice only if his co-medication had been changed. The LEV serum concentration in relation to LEV dose/body weight [level-to-dose ratio, LDR, (microgram/mL)/(mg/kg)] was calculated and compared for the most frequent drug combinations. Analysis of covariance (using age as covariate) carried out on the log-transformed data showed that co-medication had a highly significant (P < 0.001) effect on LEV serum concentrations. The median LDR of LEV was 0.32 for LEV + phenytoin, 0.32 for LEV + carbamazepine, 0.34 LEV + oxcarbazepine, 0.45 for LEV + lamotrigine, 0.46 for LEV + phenobarital, 0.52 for LEV monotherapy, 0.53 for LEV + valproic acid, and 0.54 LEV + valproic acid + lamotrigine. In co-medication with phenytoin (P < 0.001), carbamazepine (P < 0.001), and oxcarbazepine (P < 0.004), the LDR of LEV was significantly lower than it was with LEV monotherapy, whereas the LDR of LEV of patients on co-medication with valproic acid or lamotrigine did not differ significantly from the LDR of LEV of patients on LEV monotherapy (P > 0.05). Regression analysis including all 363 samples confirmed that other drugs (e.g., phenytoin, carbamazepine) lower LEV concentrations. In addition to co-medication, age had a significant effect on clearance of LEV. Children had lower LEV concentrations than adults on the same LEV dose per body weight. In contrast to other studies, our data point out that other enzyme-inducing antiepileptic drugs (e.g., phenytoin, carbamazepine) can moderately decrease LEV serum concentrations (by 20-30%). However, our observations should be confirmed by prospective pharmacokinetic studies.

Clinical Pharmacokinetics of Levetiracetam

Since 1989, eight new antiepileptic drugs (AEDs) have been licensed for clinical use. Levetiracetam is the latest to be licensed and is used as adjunctive therapy for the treatment of adult patients with partial seizures with or without secondary generalisation that are refractory to other established first-line AEDs. Pharmacokinetic studies of levetiracetam have been conducted in healthy volunteers, in adults, children and elderly patients with epilepsy, and in patients with renal and hepatic impairment. After oral ingestion, levetiracetam is rapidly absorbed, with peak concentration occurring after 1.3 hours, and its bioavailability is >95%. Co-ingestion of food slows the rate but not the extent of absorption. Levetiracetam is not bound to plasma proteins and has a volume of distribution of 0.5-0.7 L/kg. Plasma concentrations increase in proportion to dose over the clinically relevant dose range (500-5000 mg) and there is no evidence of accumulation during multiple administration. Steady-state blood concentrations are achieved within 24-48 hours. The elimination half-life in adult volunteers, adults with epilepsy, children with epilepsy and elderly volunteers is 6-8, 6-8, 5-7 and 10-11 hours, respectively. Approximately 34% of a levetiracetam dose is metabolised and 66% is excreted in urine unmetabolised; however, the metabolism is not hepatic but occurs primarily in blood by hydrolysis. Autoinduction is not a feature. As clearance is renal in nature it is directly dependent on creatinine clearance. Consequently, dosage adjustments are necessary for patients with moderate to severe renal impairment. To date, no clinically relevant pharmacokinetic interactions between AEDs and levetiracetam have been identified. Similarly, levetiracetam does not interact with digoxin, warfarin and the low-dose contraceptive pill; however, adverse pharmacodynamic interactions with carbamazepine and topiramate have been demonstrated. Overall, the pharmacokinetic characteristics of levetiracetam are highly favourable and make its clinical use simple and straightforward.

The KEEPER trial: levetiracetam adjunctive treatment of partial-onset seizures in an open-label community-based study

PURPOSE

Three randomized, placebo-controlled trials have demonstrated the safety and efficacy of levetiracetam, a new antiepileptic medication, as add-on therapy for partial-onset seizures. The purpose of this study was to gather additional safety and efficacy data on levetiracetam in the real-world setting of community-based practice.

METHODS

This was a phase IV prospective, open-label, multicenter, community-based trial. A total of 1030 patients (intent-to-treat (ITT) population) at least 16 years old (mean, 42.2 years) with partial-onset seizures were enrolled by over 300 investigators. Patients whose partial-onset seizures were inadequately controlled on their current medications had levetiracetam 500 mg bid added to their regimens. The levetiracetam dose was increased by 500 mg bid at the end of weeks 2 and 4 to a maximum dose of 1500 mg bid, unless the patient had been seizure-free during the preceding 2-week period. The dose was then to remain the same for 12 weeks. The main outcome measures were reduction in seizure frequency, global evaluation scale (GES), and adverse events.

RESULTS

During the 16 weeks of the trial, 57.9% (542/936) experienced at least a 50% reduction in the frequency of partial-onset seizures, 40.1% (375/936) experienced at least a 75% reduction, and 20% (187/936) demonstrated a 100% seizure reduction. During the last 6 weeks of the study, 66.7% (500/750) experienced at least a 50% reduction in the frequency of partial seizures, 52.4% (393/750) experienced at least a 75% reduction, and 42.1% (316/750) demonstrated a 100% seizure reduction. On the investigator-completed clinical impression rating (GES), 74.3% (734/988) of patients were considered improved, with 37% of patients showing marked improvement. The most common adverse events were somnolence, dizziness, asthenia, and headache; these events were predominantly mild-to-moderate in nature.

CONCLUSIONS

These results provide further evidence regarding the efficacy and safety of levetiracetam as adjunctive treatment for partial-onset seizures.